Fix Ubuntu apt update GPG error: repository not signed - Microsoft Store Won't Open? Step-by-Step Fix Checklist-Handling Non-Fast-Forward Pushes in Git
Before changing system settings, save your work and note the exact error text so you can compare results after each step.
Extra verification checklist
- Restart the affected app after changing permissions or configuration files.
- Test the same workflow in a clean browser profile or a temporary user account.
- Compare the result on another network if the error may be connection related.